Biosensors are devices for sensing and detecting biomolecules and operate on the basis of electronic, electrochemical, optical, and mechanical detection principles. Biosensors that include transistors are sensors that electrically sense charges, photons, and mechanical properties of bio-entities or biomolecules. The sensing can be performed by detecting the bio-entities or biomolecules themselves or through interaction and reaction between specified reactants and bio-entities/biomolecules. Using semiconductor processes, such biosensors can be manufactured as integrated circuits (ICs) and/or microelectromechanical system (MEMS).